The role of fluoride in the remineralization of carious lesions is well know. The use of agents to enhance this benefit is also well known. One such agent is strontium.
While strontium's inclusion in oral compositions containing fluoride is desirable, the agents form an insoluble precipitate unless separated before use or the strontium ions are complexed so as not to be available to form the precipitate. Strontium EDTA is such a complex.
The effect of strontium-EDTA complex in combination with sodium recinoleate and a fluoride source is found in the Journal of Dental Research (1982) 61 (3) 451-455. The combined effect of strontium and fluoride in reducing the acid solubility of enamel is also disclosed in the Journal of Dental Research (1983) 62 (10) 1049-1053. A further reference discussing the effect of strontium and fluoride Featherstone, J.D.B., "Remineralization of Artificial Carious Lesions In-vivo and In-vitro", Proceedings of Workshop, (1983) IRL Press Ltd.
The use of strontium in combination with fluoride in oral compositions is also disclosed in a number of patent references. Included among these references are U.S. Pat. No. 3,888,976, June 10, 1975 to Mlkvys disclosing an effervescent mouthwash tablet containing strontium ions and possibly a fluoride ion source. U.S. Pat. No. 4,367,219, Jan. 4, 1983 to Schole discloses dentifrices containing a combination of strontium EDTA, a recinoleate salt and a fluoride ion source. U.S. Pat. No. 4,415,549, Nov. 15, 1983 to Shah et al. discloses toothpastes containing a glycyrrhizinate salt, strontium EDTA and a fluoride ion source. Finally European Patent Application No. 0,079,611, June 6, 1983, Shah, discloses oral compositions containing a strontium EDTA complex and a fluoride ion source.
The use of other materials in oral compositions to provide a variety of benefits in combination with soluble fluoride ion sources has also been disclosed in the patent literature.
Included are certain polymers and other agents. Specific agents disclosed are polyelectrolytes such as copolymers of maleic anhydride and ethylene disclosed in U.S. Pat. No. 3,429,963, Feb. 25, 1969 to Shedlovsky. Shedlovsky also discloses polyacrylic acid having an average molecular weight of 1500 and greater. Other references disclosing polyacrylic acids in oral compositions are South African Patent No. 720898, Sept. 12, 1972 which discloses such acids having a molecular weight of from 1000 to 1,000,000; and U.S. Pat. No. 4,304,766, Dec. 8, 1971 to Chang discloses polyacrylic acid having a molecular weight in the range of 2,000 to 4,000,000 for use as a membrane to prevent the elution from teeth of previously applied agents. Finally, U.S. Pat. No. 3,956,480, to Gaffar, May 11, 1976 discloses complexes of anionic polymers (e.g., acrylic acid) and a cationic therapeutic agent (e.g., chlorhexidine) as anticalculus agents.
In spite of the many disclosures of strontium, fluoride ions and polyacrylic acids in the prior art, there is lacking a suggestion to combine these agents in a single oral composition. Strontium ions form a complex with the polyacrylic acid thereby not being able to form a precipitate with fluoride.
It is therefore an object of the present invention to provide oral compositions which combine a polyacrylic acid polymer or copolymer, strontium and fluoride.
It is a further object of the present invention to provide a more effective anti-caries composition.
It is still a further object of the present invention to provide a more effective method of applying fluoride to tooth enamel and dentin.
These and other objects will become more clear from the detailed description which follows.
All percentages and ratios used herein are by weight unless otherwise specified.